Effect of physical properties of milk fat globules on Brucella ring test sensitivity

Variations in Brucella milk ring test reactions have been attributed to size and disparity in size of fat globules, fat content of milk, inhibitory factors, and cream-rising capacity. Physical properties of milk fat globules were studied in individual milk samples that had diverse sensitivities for detection of Brucella agglutinins. Size or disparity of globule size could not be correlated with the milk ring test sensitivity. Inhibitory and enhancing creaming factors could be transferred from the cream to the skim milk and reacted with other cream to show changes in sensitivity. The proportion of clustered milk fat globules was related directly to the quantity of agglutinins detected by the test. Sensitivity of the test was attributed to a fat globule agglutinin that caused clustering and to an inhibitory factor.